1. Field of the Invention
This invention relates to a novel liquid composition which is useful in automatic glasswashing machines and effectively cleans glassware while having the property of being low-foaming in both unheated and heated water.
2. Description of the Prior Art
Automatic equipment for washing glassware is known; such equipment is usually used by restaurants and the like, and is capable of washing, for example, from 1,500 to 4,000 glasses per hour, typically using a cycle time of about 1 minute.
It has been customary, in the operation of such equipment, to use hot water, i.e., water at a temperature of 130.degree. to 160.degree. F. The use of water at such a temperature improves the washing action but has the drawback of imposing an energy requirement. In light of the current energy crisis, this is undesirable. Perhaps the greatest obstacle to the development of a suitable detergent composition, capable of washing glasses in a commercial glass-washing machine with the use of room-temperature water, has been the consideration that it is desirable to use a nonionic surfactant which will provide adequate detergency in conjunction with a substantial proportion of caustic (sodium hydroxide and/or potassium hydroxide), but there are usually considerable difficulties in respect to (a) getting the nonionic surfactant to be stable in and compatible with the aqueous caustic comprising a substantial proportion of the remainder of the composition and (b) obtaining a composition which is satisfactorily low-foaming. In general, the non-ionic surfactants are more soluble in cold water than in hot water, and it is generally true that at lower water temperatures, they are higher-foaming. The development of a satisfactory composition based upon caustic, water, and low-foaming non-ionic surfactant is, accordingly, a challenging problem.
It may also be taken as known from U.S. Pat. No. 3,956,161 that it is possible to making cleaning compositions which contain water, alkali such as 10 to 30 weight percent of sodium hydroxide, 2 to 6 weight percent of nonionic surfactant, and (as a hydrotrope or solubilizing agent for the nonionic surfactant) 2 to 10 weight percent of alkali-metal salt of a C.sub.21 dicarboxylic acid. The patent teaches the desirability of using such a composition when low foaming is desired, but it does not give any teaching of how to meet the extremely stringent lowfoaming requirements of a process for machine washing of glassware with water at about 50.degree. to 110.degree. Fahrenheit, while maintaining adequate detergency.